Radiotelephony.



C. R. ENGLUND. RADIUTELEPHONY. APPLICATION FILED m. n. 1916.

1,258,548. Patented Mar. 5,1918.

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" the radiated wave 1) STATES PATENT onnron.

GMT; JR. ENGL'UNID, OF EAST ORANGE, NEW JERSEY, ASSTGNOB T WESTERNELECTRIC comm, rnconrona'rnn, or new YonK, IT. 1., A conrona qrlmronx.nanro'rnnnrnonr.

Speeificationcf Letters Patent.

Patented Mar. a, 1918.

Application filed March 11, 1916. Serial No. 83,504.

To all whom may concern:

Be it known that I, CARL R. ENGLUND, a citizen of the United States,residing at East Orange, in the county State of New Jersey, haveinventedcertain new and useful Improvements in Radiotelephony, of whichthe following is a full, clear, concise, and exact description.

This invention relates to radio telephony, and in particular to a systemof transmission in which only the modulated portion of a high frequencywave is radiated from the antenna.

in radio telephony it has been customary to establish in a circuit ahigh frequency oscillation and to modulate the amplitude of thisoscillation in accordance with a signal to be transmitted. Now, it iswell-known that when a high frequency carrier wave of frequency C ismodulated in accordance with a s1gnal wave of frequency S, the resultant wave radiated from the antenna is made up of three parts offrequencies CS, U and (3-1-55, which components may be considered to betransmitted simultaneously through the ether. It has been proposed asdescribed in British specification No. 17,170 of 1916 of which theserial number under the new British system of consecutive numbering, is102,503, to eliminate from the antenna the unmodulated component offrequency t), and to transmit only the modulated portions represented bythe other two components. When this method is adopted is spoken of as apure modulated wave. The great advantage of this method is that thewaste of power represented by currents of frequency 0 in the antenna iseliminated, and that there is some gain in the quality of receivedoscillation. in order to receive signals sent in this manner it isnecessary to include at the receiving station, in addition to the usualapparatus, a small enerator capable of delivering currents o theelminated frequency C, but since only a very small amount of power ofthis frequency is required at the receiving station, the auxiliarygenerator at that station need have but an extremely small power output.

in the s ecification above referred to a 'certain metihod of eliminatingthe unmo ulated component of the carrier wave is given, and thisinvention proposes still anat other-- way of accomplish ng this purpose,

of Essex and 'oscillatlon of carrier namely, by superposing upon themodulated wave before it reaches the antenna an oscillation of carrierfrequency which is equal in amplitude but opposite in phase to thefrequency which represents the unmodulated portion of the wave to betransmitted. By this means the component to be eliminated from theantenna is neutralized in the apparatus between the primary modulatingsource and the antenna. The invention will be more particularlydescribed in connection with the drawing, in which Figure 1 represents atransmitting station constructed in accordance with this invention andFig. 2 shows a form of receiving station by which the modulated wavesmay be received. This receiving station forms no part of this invention.

Referring to Fig. 1, 1 is a generator of oscillations of the frequency Cand 2 a trans former by means of which these oscillations are impressedupon the input circuit of a thermionic modulator 8. 4. is a microphonecircuit, the variations of current in which are impressed upon the sameinput circuit through the transformer 5. The result of this arrangementis, as is now well-known, to produce in the output circuit of themodulator 3 a high frequency current whose amplitude is modulated inaccordance with the alternating currents set up in the microphonecircuit. This output circuit is connected through transformer 6 to thecommon input circuit of a number of thermionic amplifiers 7 arranged inparallel, their common output circuit being coupled through transformer8 to the radiating antenna 9.

The system so far described is characterized by the fact that currentsof all three of the above mentioned frequencies occur in the antenna 9.By means of the apparatus next to be described the component offrequency 0 is prevented from reaching the antenna by being neutralizedin the input circuit of the amplifier 7. To accomplish this, the inputcircuit of the amplifier 10 is connected through an autotransformer 11to the terminals of the generator 1, the purpose of this autotransformerconnection be-' g" emat te ampli ers 7. It will be clear that thislatter voltage will have the frequency C of oscillations "produced bythe generator" 1 and that. these'inay be so regulated as to intensityantenna 9. In case the amplifier 10 or the. phase regulating device 12are not so ad-.

just'ed that the neutralizing current is exactly opposite in phase orequal in intensity to the component of frequency 0 of, the modulatedcurrent, a small portion of the said component of frequency C may not beneutralized. In such a case, the system would be operative, but lessefficient, as some energy' would he radiated in the form of waves offrequency 0. The expressions equal in intensity and opposite in phaseshould,

j therefore, be taken to mean substantially equal in intensity andsubstantially opposite in phase.

Referring to Fig. 2, 14 is a receiving antemia coup ed to a resonantcircu t 15 tuned to,.the frequency 0 of the waves to be recived. 16 isathermionic detector Whose output circuit is connected through atransformer to thetranslating device 17. It will be clear that the Wavesreceived by this syster'rriwill lack the component of frequency G, andthe function of the auxiliary generator 18 is to supply smalloscillations of this frequency. The circuit of this generator maybecoupled in'iany suitable manner to the antenna 14; or to the resonantcircuit 15.

2 Although this invention has. been described as applying toradio.telephony, it will be clear to those skilled in the art'thata wiretelephone line may be substituted for the antenna -9 without departingfrom the spirit of" this invention. It will further then afipplied tothe common input circuit of be obvious'that many other circuit arrangements may be devised by means of which the oscillation of frequency ,0may .be neutralized in the input circuit of the amplifier 7. What isclaimed is:

1. The method of preventing the radia tion of the unmodulated componentof. a signaling wave which consists in superposing upon said wave anunmodulated Wave of equal value,- but of phase opposite to that of thesaid unmodulated component.

2. The method of preventing the radiation of the unmodulated componentof a signaling wave which consists in opposing said compunent by anequal wave.

3. A radio transmitting system comprising in' combination means forgenerating and modulating high frequency oscillations means forimpressing upon said modulated oscillations an unmodulated oscillationof opposite phase, and means for amplifying and transmitti g theresultant of said oscillations.

4. A radio transmitting system comprising in combination means forgenerating and modulating high frequency oscillations, means forneutralizing the, unmodulated component of said modulated wave, andmeans for amplifying and transmitting the modulated portion of saidwave.

5 In a radio transmitting system, the combination of means forgenerating high frequency oscillations in two circuits, means formodulating the oscillationsof one of said circuits, means for changingthe phase of said unmodulated oscillations in the other circuit so thatit is substantially opposite of said-modulated oscillations, and meansfor impressing said modulated and unmodulated oscillations of changedphase upon a third circuit.

' In witness whereof, I hereunto subscribe my name this 9th day of MarchA. D.,.1916.

-to the phase of the modulated-component ;oaana. EueLUNn;

